1. Field of the Invention
The present invention relates to stability problems associated with large scale controllable supplies such as electrical power, and more specifically, it relates to systems and methods for controlling the demand on such large scale supplies.
2. Description of Related Art
Large scale systems such as electrical power, water and natural gas utilities, characterized by centrally controlled supply and distributed autonomous demand, are typically susceptible to stability problems. In the past, some manual and automated methods have been used for centralized control of electric power demand (as opposed to autonomous demand control). Under-frequency and under-voltage relays have been used to protect power generation equipment on systems, but are not used for demand control.
A key challenge to real time grid control is instability caused either by loss of generation capacity or by loss of electrical load. These losses cause rapid decreases or increases in system frequencies and voltages. The time scales of these system transients are so short that human intervention is often not possible. Accordingly, autonomous frequency and voltage relays currently deployed in transmission and distribution systems typically respond conservatively by shedding more load or generation than may be necessary to stabilize the system. Occasionally unanticipated interactions among them lead to large-scale, protracted blackouts.
Centrally controlled demand response technologies have been proposed under the rubric of homeostatic control. However, no practical and scalable implementations have been realized due in part to the complexity and cost of required communication and control systems.